To a motor of a hybrid electric vehicle (HEV), an electric vehicle (EV) or the like, Nd—Fe—B based magnets are applied mainly. Since a high heat resistance is required of such a use, (Nd, Dy)—Fe—B based magnets in which part of neodymium (Nd) is replaced by dysprosium (Dy) are used. In a full-scale propagation of motors for HEV and EV, a permanent magnet in which Dy being a rare element is not used is required. Meanwhile, it is known that Sm—Co based magnets have a superior heat resistance without using Dy. As the Sm—Co based permanent magnets, there are known SmCo5 type magnets based on a binary system intermetallic compound of Sm and Co, and Sm2Co17 type magnets which have a two-phase separation structure of a Th2Zn17 crystal phase and a CaCu5 crystal phase and has a magnet property by a magnetic coercive force exhibiting mechanism of a magnetic domain wall pinning type.
The Sm2Co17 type magnet is superior in a magnetic coercive force and a maximum magnetic energy product compared with the SmCo5 type magnet, and has a superior heat resistance due to a high Curie temperature. Since the Sm—Co based magnet contains much Co, the Sm—Co based magnet is of high cost, and further a magnetization of the Sm—Co based magnet is smaller compared with that of the Nd—Fe—B based magnet. For an improvement of the magnetization of the Sm2Co17 type magnet, increasing a content of Fe in the Sm2Co17 type magnet is effective, and by increasing the Fe content, it is possible to reduce a cost of the Sm2Co17 type magnet. However, increasing the Fe content incurs a destabilization of a TbCu7 crystal phase (high-temperature phase) being a precursor of the Sm2Co17 type magnet, and consequently, the two-phase separation structure of the Th2Zn17 crystal phase and the CaCu5 crystal phase cannot be obtained.